Modular thyristor-based rectifier circuits

Abstract

Power conversion apparatus for controllably converting alternating current (AC) to direct current (DC). An example apparatus includes multiple AC sources, galvanically isolated from one another, and multiple bridge rectifier circuits, including one or more controllable bridge rectifier circuits, where each bridge rectifier circuit has respective AC-side terminals and DC-side terminals and each bridge rectifier circuit is connected to a corresponding one of the AC sources via its AC-side terminals. The DC-side terminals are connected so that the outputs of the bridge rectifier circuits are combined in series. A control circuit is configured to individually control each controllable bridge rectifier circuit to selectively operate in a regulator mode, whereby a non-zero voltage less than or equal to the maximum rectifier voltage is provided, and a bypass mode, whereby the controllable bridge rectifier circuit provides a negligible voltage to its DC-side terminals and draws negligible current from its corresponding AC source.

What is claimed is: 
     
       1. A power conversion apparatus for controllably converting alternating current (AC) to direct current (DC), the power conversion apparatus comprising:
 a plurality of AC sources galvanically isolated from one another; 
 a plurality of bridge rectifier circuits, including one or more controllable bridge rectifier circuits, wherein each of the plurality of bridge rectifier circuits has respective AC-side terminals and DC-side terminals and each of the plurality of bridge rectifier circuits is connected to a corresponding one of the plurality of AC sources via each bridge rectifier circuit at respective AC-side terminals, and wherein the DC-side terminals are connected so that outputs of the plurality of bridge rectifier circuits are combined in series; and 
 a control circuit configured to individually control each of the one or more controllable bridge rectifier circuits to selectively operate in (i) a regulator mode, whereby a non-zero voltage less than or equal to a maximum rectifier voltage is provided by the DC-side terminals of each of the one or more controllable bridge rectifier circuits, and (ii) a bypass mode, whereby each of the one or more controllable bridge rectifier circuits provides a nominally zero voltage to the DC-side terminals of the one or more controllable bridge rectifier circuits and draws a nominally zero current from the corresponding one of the plurality of AC sources connected to the controllable bridge rectifier circuits, even while one or more of the plurality of bridge rectifier circuits are operating in regulator mode; 
 wherein the plurality of bridge rectifier circuits includes at least two controllable bridge rectifier circuits, wherein the regulator mode for each of the at least two controllable bridge rectifier circuits comprises a voltage regulating mode and a full output mode, and wherein the control circuit is configured to control the at least two controllable bridge rectifier circuits so that only one of the controllable bridge rectifier circuits is operating in voltage regulating mode at any given time, while each of the remaining controllable bridge rectifier circuits is operating in either bypass mode or full output mode. 
 
     
     
       2. The power conversion apparatus of  claim 1 , further comprising a transformer having a primary winding configured for connection to one or more of the plurality of AC sources and at least one output winding, wherein at least one of the plurality of bridge rectifier circuits has each bridge rectifier circuit at respective AC-side terminals connected across the at least one output winding. 
     
     
       3. The power conversion apparatus of  claim 2 , wherein the respective AC-side terminals of one of the plurality of bridge rectifier circuits is conductively connected to the primary winding. 
     
     
       4. The power conversion apparatus of  claim 1 , wherein one or more of the plurality of AC sources is a winding of a rotating machine. 
     
     
       5. The power conversion apparatus of  claim 1 , wherein at least one of the plurality of bridge rectifier circuits is a diode rectifier circuit. 
     
     
       6. The power conversion apparatus of  claim 1 , wherein the control circuit is configured to control the at least two controllable bridge rectifier circuits so as to successively operate a different one of the at least two controllable bridge rectifier circuits in voltage regulating mode, while each of the remaining controllable bridge rectifier circuits is operating in either bypass mode or full output mode. 
     
     
       7. The power conversion apparatus of  claim 1 , wherein one of the one or more controllable bridge rectifier circuits is a thyristor bridge rectifier, and wherein the control circuit is configured to control the thyristor bridge rectifier to operate in bypass mode by triggering a thyristor in each one of two arms of a single phase leg to conduct simultaneously. 
     
     
       8. The power conversion apparatus of  claim 7 , wherein the control circuit is configured to control the thyristor bridge rectifier in bypass mode by successively triggering thyristors so as to rotate a bypass leg among multiple phase legs of the thyristor bridge rectifier. 
     
     
       9. A method for controllably converting alternating current (AC) to direct current (DC), the method comprising:
 providing a plurality of AC sources, galvanically isolated from one another; 
 providing a plurality of bridge rectifier circuits, including one or more controllable bridge rectifier circuits, wherein each of the plurality of bridge rectifier circuits has respective AC-side terminals and DC-side terminals and each of the plurality of bridge rectifier circuits is connected to a corresponding one of the plurality of AC sources, and wherein the DC-side terminals are connected so that outputs of the plurality of bridge rectifier circuits are combined in series; and 
 individually controlling each of the one or more controllable bridge rectifier circuits to selectively operate in a regulator mode, whereby a non-zero voltage less than or equal to a maximum rectifier voltage is provided by each of the one or more controllable bridge rectifier circuits, and a bypass mode, whereby each of the one or more controllable bridge rectifier circuits provides a nominally zero voltage to the DC-side terminals of the one or more controllable bridge rectifier circuits and draws a nominally zero current from the corresponding one of the plurality of AC sources connected to the controllable bridge rectifier circuit; 
 wherein the plurality of bridge rectifier circuits includes at least two controllable bridge rectifier circuits, wherein the regulator mode for each of the at least two controllable bridge rectifier circuits comprises a voltage regulating mode and a full output mode, and wherein the method further comprises controlling the at least two controllable bridge rectifier circuits so that only one of the controllable bridge rectifier circuits is operating in voltage regulating mode at any given time, while each of the remaining controllable bridge rectifier circuits is operating in either bypass mode or full output mode. 
 
     
     
       10. The method of  claim 9 , wherein at least one of the bridge rectifier circuits is a diode rectifier circuit. 
     
     
       11. The method of  claim 9 , wherein the method comprises controlling the at least two controllable bridge rectifier circuits so as to successively operate a different one of the at least two controllable bridge rectifier circuits in voltage regulating mode, while each of the remaining controllable bridge rectifier circuits is operating in either bypass mode or full output mode. 
     
     
       12. The method of  claim 9 , wherein one of the one or more controllable bridge rectifier circuits is a thyristor bridge rectifier, and wherein the method comprises controlling the thyristor bridge rectifier to operate in bypass mode by triggering a thyristor in each one of two arms of a single phase leg to conduct simultaneously. 
     
     
       13. The method of  claim 12 , wherein the method comprises controlling the thyristor bridge rectifier in bypass mode by successively triggering thyristors so as to rotate a bypass leg among multiple phase legs of the thyristor bridge rectifier.